<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>老八选择器</title>
    <style>
        .waring{
           font-size: 40px;
        }
        .red{
            color: red;
        }
    </style>
</head>
<body>
    <p>练习</p>
    <p class="waring red">练习变大变颜色</p>
    <span class="warning">练习变大</span>
    <span class="red">练习变色</span>
</body>
</html>